The scaling of optoelectronic devices to smaller and smaller spatial dimensions results, at least theoretically, in an increased device density and reduced optical system size. Additionally, and perhaps more importantly, there is also a corresponding increase in the strength of light-matter interactions with reduced size scale, an effect which can dramatically alter the power, speed, and efficiency of an optical device. Geometry below or at the wavelength scale also plays an intricate role in optics, as demonstrated recently in the work on engineered photonic crystals and so-called "left-handed" materials. In this talk I will discuss the application of geometry and scale in optical structures to several different areas of our own current research: chip-scale atom-cavity QED, plasmon-optics, and silicon microphotonics.